- Heat oven to 200 degC. Line 12 holes of a standard muffin pan with paper cases. Place egg in a bowl and beat lightly. Add oil, sugar, milk, sour cream and vanilla to beaten egg and stir to combine.
- Sift flour, baking soda and cinnamon into a bowl. Make a well in the centre and pour the wet ingredients and the rhubarb into the well. Stir just enough to combine.
- Spoon batter into paper cases to fill to three-quarters. Sprinkle with raw sugar and bake for 25 minutes or until golden brown and a skewer inserted into the centre of one muffin comes out clean.